Installing nova-docker with devstack

This is a long-form response to this question, and describes
how to get the nova-docker driver up running with devstack
under Ubuntu 14.04 (Trusty). I wrote a similar post for Fedora
21, although that one was using the RDO Juno packages, while this
one is using devstack and the upstream sources.

Docker by default creates its socket (/var/run/docker.socket) with
root:root ownership. We’re going to be running devstack as the
ubuntu user, so let’s change that by editing /etc/default/docker
and setting:

Install nova-docker rootwrap filters

Starting a Docker container

Now that our environment is up and running, we should be able to start
a container. We’ll start by grabbing some admin credentials for our
OpenStack environment:

$ . openrc admin

Next, we need an appropriate image; my larsks/thttpd image
is small (so it’s quick to download) and does not require any
interactive terminal (so it’s appropriate for nova-docker), so let’s
start with that: